I took my MPX merlin with me to the Viking Race in case of a calm day. I had the chance to maiden it, then to fly it few times, and I must say that I'm impressed by this little bird.
The sink rate is higher than a "normal" glider which is normal considering the size of the plane, but the handling is great and the combo sold by Natterer Modelbau is perfect, especially when using a 3S Hyperion G3 850 mAh.
With this battery, the climbing is amazing, almost vertical. The battery also sustain the discharge without collapsing which is good. We organised an informal F3F race (2 rounds) with 6 pilots and thanks to the battery, I won the comp, with a 47s in the second round. Other pilots had less perfomant batteries :)
So I definitively recommend this battery:
You can find the specifications here
To finish here is a video (from Thibaud Ringenbach) of my first run with the Merlin. I did a 52s with a big cut. But you will see how good is this little bird :) ... look at the turns !